Gas-venting arrangement

ABSTRACT

The invention relates to a gas-venting arrangement in a paint-toning machine. A dispensing device ( 20 ) comprises an at least substantially vertical-shafted dispensing pump ( 20 ) connected through a suction pipe ( 13 ) to the inside of a colour paste container and through a dispensing pipe ( 17 ) to a dispensing nozzle. The pump ( 20 ) comprises a dispensing cylinder ( 21 ) and inside it a reciprocating displacement element ( 14 ). The lower end of the displacement element ( 14 ) in the lower extreme position of its dispensing movement is either level with or past the upper edge ( 15 ) of the dispensing pipe ( 17 ) opening into the dispensing cylinder ( 21 ), and the positions of the suction and dispensing pipes ( 13, 17 ) and the lower end of the displacement element ( 14 ) in said extreme position are such that they together form a substantially horizontal flow path or one ascending in the direction (A) of the dispensing flow.

FIELD OF THE INVENTION

[0001] The present invention relates to a gas-venting arrangement in a paint-toning machine which comprises one or more containers for storing colour paste or the like, and a dispensing device connected to each container for dispensing the colour paste from the colour paste container, the dispensing device comprising an at least substantially vertical-shafted dispensing pump connected through a suction pipe to the inside of the colour paste container and through a dispensing pipe to a dispensing nozzle and comprising a dispensing cylinder and inside it a reciprocating replacement element, whereby the dispensing is controlled by a suction valve arranged in the suction pipe and a dispensing valve arranged in the dispensing pipe.

[0002] Paint-toning machines as described above are known from U.S. Pat. Nos. 4,708,269; 5,445,195 and 5,938,080, for instance.

[0003] In dispensing colour paste, a pump 8 based on admission and outward, i.e. dispensing, strokes, as shown in FIG. 1 of the attached drawing, is used in general. Such a pump usually has a valve with a sliding slide valve 3 having a small inner volume. In some cases, different poppet valve modifications are also used as the valves. Toning machines usually have several paste containers 1 and they are located as close together as possible so that the assembly would not require too much space. The most common construction method is to locate the valve 3 substantially close to the bottom surface of the container 1 and the pump 8 immediately above it. The plunger 4 of the pump then moves upward during an admission stroke and downward towards the valve during an outward, or dispensing, stroke. The arrangement provides the shortest possible suction pipe 2 length and the highest possible hydrostatic pressure caused by the height of the natural liquid level of the colour agent to facilitate the entry of the slow-moving colour paste to fill the pump 8 during an admission stroke.

[0004] The above-mentioned construction method has been in use in manually-operated toning machines during more than 40 years. A corresponding construction has also passed down to the automatic toning machines, and it has been very common in them during more than 25 years. A serious disadvantage in the construction is the imprecision of the smallest doses, the reason for which has not been understood up till now. On the other hand, the devices have been relatively inexpensive and thus a great precision has not been expected of them.

[0005] A practical study of the matter has been very difficult because of the difficult behaviour of colour agents. To prevent imprecision, the usual method has been to make the valve as small in volume as possible. The imprecision problem in small doses in particular has this way been only passably solved.

[0006] Manufacturers of toning systems have, however, wanted to be able to dispense smaller and smaller doses precisely. This would provide a possibility to develop stronger colour pastes than before and make the dispensing faster. At the same time, it would be possible to develop lighter tones than before and to tone them precisely in even smaller canisters. This would, as a whole, also provide a considerable advantage in that the filling interval of machines would become longer and less transport and storage space would be needed.

BRIEF DESCRIPTION OF THE INVENTION

[0007] It has been discovered according to the invention that the above-mentioned precision problem related to dispensing small doses in particular can be solved by means of a gas-venting arrangement, which is characterized in that the lower end of a displacement element in the lower extreme position of the dispensing movement of the element with respect to earth gravity is either level with the upper edge of a dispensing pipe opening into a dispensing cylinder or past it, and that the mutual height positions of the suction and dispensing pipes and the lower end of the displacement element in said extreme position are such that they together form a substantially horizontal flow path or a flow path ascending in the direction of the dispensing flow.

[0008] In the present pasta dispensing devices according to FIG. 1, the dispensing errors have been detected to originate from the structure of the conduit between the suction valve 3, the dispensing pump 8 and the dispensing valve 3. This structure easily accumulates gas bubbles 7 and, due to the compressibility of gas, causes significant errors in dispensing. Gas bubbles 7 accumulate especially to the bottom surface of the lower end of the displacement element 4 of the dispensing pump already when the machine is taken into use and also when paste is sucked by means of this displacement element, these gas bubbles cannot exit said space in a conventional suction pump construction. When these gas bubbles expand during the suction phase and compress during the dispensing phase by effect of the displacement element, an error is caused in the amount of paste moved by the displacement element, and, naturally, the smaller the dispensing amount, the bigger the relative error.

[0009] When using the dispensing pump construction of the invention, all gas bubbles on the bottom surface of the lower end of the displacement element when the machine is taken into use will immediately at the end of the first dispensing phase move on towards the dispensing valve and thus do not decrease the dispensing precision during the next suction phase. Similarly, all gas bubbles which along with the paste being dispensed end up on the bottom surface of the lower end of the displacement element through the suction valve can move on towards the dispensing valve and do not remain to decrease the dispensing precision of the dispensing pump.

BRIEF DESCRIPTION OF THE FIGURES

[0010] In the following, the gas-venting arrangement of the invention is described in greater detail with reference to the attached drawing, in which

[0011]FIG. 1 shows a schematic diagram illustrating dispensing in a paint-toning machine of prior art,

[0012]FIG. 2 shows a schematic diagram illustrating dispensing in a paint-toning machine of the invention during an admission stroke,

[0013]FIG. 3 shows a schematic diagram illustrating dispensing in a paint-toning machine of the invention during the end of a dispensing stroke, and

[0014]FIG. 4 shows a variation of the paint-toning machine of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0015]FIGS. 2 and 3 of the attached drawing show a schematic diagram of the structure and operating principle of a paint-toning machine of the invention. FIG. 2 especially shows the general structure of the machine with respect to colour paste dispensing in particular. Basically, the machine comprises one or more containers 11 for colour paste or another liquid to be dispensed. Dispensing means are connected to each container 11, the main components of which are a suction valve 12, a dispensing pump 20 and a dispensing valve 16.

[0016] The dispensing pump 20 is a displacement pump having a substantially vertical shaft. This means that at least basically, the movement of the displacement element of the pump is in the direction of earth gravity or in a direction which only differs from it to some extent. This dispensing pump 20 comprises a dispensing cylinder 21 and inside it, a reciprocating displacement element 14, which in the following will be referred to as a plunger regardless of whether it is moved by a plunger rod or a bellows-type unit.

[0017] The dispensing pump 20 is connected to the container 11 through a suction pipe 13 which is connected to the bottom part of the container 11, most preferably to its bottom. A suction valve 12 is arranged to this suction pipe 13 for controlling the direction of travel of the paste during dispensing. The direction of travel of the colour paste during dispensing is marked by arrow A. FIG. 2 shows a dispensing situation in which paste is being sucked into the dispensing pump 20 from the container 11. The suction valve 12 is then open and paste can flow from the paste container 11 to the dispensing pump 20. When moving the plunger 14 in the direction of arrow B in FIG. 2, the paste moves from the container 11 and fills the cylinder 21 to the extent that the plunger 14 is lifted.

[0018] According to the invention, the essential in the situation of FIG. 2 is that the top edge of the suction pipe 13 starting from the suction valve 12 is either level with or lower than the bottom surface of the lower end of the plunger 14 in all dispensing positions of the plunger 14. Gas bubbles 19 in the sucked paste can then move from the suction valve 12 and suction pipe 13 to the suction pump 20.

[0019]FIG. 3 shows the paint-toning machine of FIG. 2 in a situation in which the dispensing plunger 14 is in its lowest extreme position, i.e. the position it reaches at the end of the dispensing phase. In this situation, the suction valve in the suction pipe 13 is closed and the dispensing valve 16 in the dispensing pipe 17 starting from the dispensing pump 20 is open to allow the liquid being dispensed to flow through the dispensing pipe 17 to the dispensing nozzle 18.

[0020] It is essential for the invention, as also shown in FIG. 3, that in this situation in which the dispensing plunger is at its lowest dispensing position, the bottom surface of the lower end of the dispensing plunger 14 is either level with or lower than the top edge 15 of the dispensing pipe 17. The gas bubbles 19 can then move on from the dispensing pump 20 in the direction of the dispensing nozzle 18. Thus, the gas bubbles do not remain in the dispensing pump, which would significantly decrease the dispensing precision.

[0021] In the embodiment of the invention according to FIGS. 2 and 3, it has been possible to leave out entirely a separate vertical channel collecting gas bubbles between the pump and valve. The described arrangement of the invention guarantees that at the very end of the dispensing, the liquid being dispensed flows a short distance to the side and/or up with respect to gravity. This essential change in the flow direction of the colour paste in the immediate proximity to the plunger 14 makes the gas bubbles 19 bound to the colour paste flow along with the colour paste being dispensed away from the pump 20. With a suitable timing of the suction and dispensing valve 12 and 16 operation, it is possible to make these continuously forming and accumulating gas bubbles 19 move away from the pump 20 through the nozzle 18. Making this operation automatic and continuous during dispensing, it efficiently prevents the accumulation of gas bubbles inside the pump 20, in the valves 12 and 16 or in the dispensing pipe 17 and nozzle 18. Said arrangement makes it possible to eliminate the imprecision of small-dose dispensing occurring in earlier corresponding paint-toning machines.

[0022] The outflow of gas bubbles described above can further be improved by an arrangement of FIG. 4, in which the machine of FIGS. 2 and 3 is slightly tilted in such a manner that the dispensing nozzle side end of the machine is lifted slightly upward. By means of this arrangement, the exiting of gas bubbles can be further intensified. In this arrangement, the movement of the gas bubbles resembles the behaviour of the bubble in a builder's level and is a very efficient way of removing the generated gas bubbles. In practical experiments, the arrangements of the invention have provided a substantial improvement in dispensing precision. At the same time, it has been possible to keep the space utilisation of the remaining construction of the machine excellent. Thus, the construction method of the invention makes it possible to significantly improve dispensing precision especially with small doses and in principle with nearly no additional costs, when the dispensing pump and the channels connected to it are implemented according to the invention.

[0023] The paint-toning machine of the invention and its operation are above described by means of two exemplary embodiments only, and it is to be understood that several modifications can be made to it without departing from the scope of protection defined by the attached claims. 

1. A gas-venting arrangement in a paint-toning machine which comprises one or more containers (11) for storing colour paste or the like, and a dispensing device (20) connected to each container for dispensing the colour paste from the colour paste container (11), the dispensing device comprising an at least substantially vertical-shafted dispensing pump (20) connected through a suction pipe (13) to the inside of the colour paste container and through a dispensing pipe (17) to a dispensing nozzle (18) and comprising a dispensing cylinder (21) and inside it a reciprocating replacement element (14), whereby the dispensing is controlled by a suction valve (12) arranged in the suction pipe (13) and a dispensing valve (16) arranged in the dispensing pipe (17), characterized in that the lower end of the displacement element (14) in the lower extreme position of the dispensing movement of the element with respect to earth gravity is either level with the upper edge (15) of the dispensing pipe (17) opening into the dispensing cylinder (21) or past it, and that the mutual height positions of the suction and dispensing pipes (13, 17) and the lower end of the displacement element (14) in said extreme position are such that they together form a substantially horizontal flow path or a flow path ascending in the direction (A) of the dispensing flow.
 2. An arrangement as claimed in claim 1, characterized in that the top edges of the suction and dispensing pipes (13, 17) and the lower end of the displacement element (14) in the lower extreme position of its dispensing movement are located substantially on the same line which at least slightly ascends in the direction of the dispensing pipe (17).
 3. An arrangement as claimed in claim 1 or 2, characterized in that the displacement element (14) is a plunger.
 4. An arrangement as claimed in claim 1 or 2, characterized in that the displacement element (14) is one that moves with a bellows. 